In this article we’ll cover the disc brake system, one of the hydraulic brake types used in vehicles. We’ll go over disc brakes’ working principle, parts, and advantages and disadvantages.
Used more often and more efficiently than drum brakes, disc brakes include rotors bolted to the wheel hub and calipers on which the brake pads are mounted.
Pressure transmitted from the brake pedal, through the master cylinder, by the hydraulic fluid, also known as brake fluid, squeezes the caliper’s disc pads onto the rotor. This process produces friction between the pad and rotor that forces the vehicle to slow down or stop.
How Disc Hydraulic Brakes Work
- When the brake pedal is pressed, high-pressure fluid from the master cylinder pushes the piston outward.
- This piston pushes the brake pad against the rotating disc.
- When the inner brake pad touches the rotor, the fluid pressure applies force, and the caliper moves inward, pulling the outer brake pad toward the rotating disc, which then touches the disc as well.
- Both brake pads press against the rotating disc, and a large amount of friction is generated between the pads and the rotating disc, which slows down and stops the vehicle.
- When the brake pad is released, the piston moves inward, the brake pad moves away from the rotating disc, and the vehicle starts moving again.
A video animation showing how disc brakes work (above)
The structure of the servo seen in the previous animation (above)
Parts of Disc Hydraulic Brakes
Wheel Hub: The disc rotor is attached to the wheel hub and rotates together with it. The vehicle’s wheel is bolted to the wheel hub.
Caliper Assembly: The brake pad touches the rotor disc, and the vehicle’s speed decreases due to the friction between the brake pad and the rotor disc.
Disc Rotor: Attached to the wheel hub and rotates together with the wheel. It’s the surface the brake pads make contact with. When you press the brake, pressurized brake fluid pushes the pistons inside the caliper, forcing the brake pads toward the rotor. When the brake pads press on both sides of the disc, friction stops the wheel from turning. Rotors can be solid or ventilated. Ventilated ones have more surface area and can dissipate heat more easily
Number of Caliper Pistons
In performance-oriented disc brakes, calipers with more than 2 pistons can be used for more even pressing force.
Ventilated Disc Design
Ventilated (drilled/slotted) disc brakes dissipate heat faster, delaying brake fade.
Consistent Braking Distance
Disc brakes provide a more consistent stopping distance even under repeated hard braking.
Advantages of Disc Brakes
- Disc brakes are lighter than drum brakes.
- Since the braking surface is exposed to air, it provides better cooling.
- It has an even pressure distribution.
- Easy replacement of brake pads.
- Disc brakes are self-adjusting brakes.
Weaknesses of Disc Brakes
- Disc brakes are generally more costly than drum brakes.
- Higher pedal pressure is required to stop the vehicle, and the brake system is equipped with a vacuum booster.
- It’s difficult to fit a suitable parking brake attachment with this system.
In this article, we covered the structure, parts, and working principles of disc hydraulic brakes. We tried to explain how a disc hydraulic brake works, supported by sample images and videos. Looking forward to seeing you in new articles.
Related Questions
When the brake pedal is pressed, pressurized fluid from the master cylinder pushes the piston inside the caliper outward. This piston motion pushes the pad directly against the rotating rotor, generating friction.
Pressure from only one side would slow the rotor unevenly and with weaker force. Both pads squeezing the rotor from both directions provides stronger and more balanced braking.
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